秸秆还田种类对稻田N2O排放及硝化反硝化微生物的影响

以太湖流域典型单季稻田的原状土柱为研究对象,通过设置温室土柱试验,同步监测3种秸秆(水稻秸秆RS、小麦秸秆WS、玉米秸秆MS)施用下水稻各生长期N₂O排放、水稻产量和土壤理化因子,同时定量化分析多个N₂O排放相关菌群及功能基因的丰度,以阐明N₂O排放对不同种类秸秆施用引发的微生物响应机制,筛选控制单季稻田N₂O减排增效最佳的秸秆种类。结果表明：与对照相比,RS、WS和MS处理下水稻生长期N₂O排放量分别增加162.32%、107.11%和9.48%,其中RS处理显著高于MS处理。水稻生育期内,土壤氨氧化菌(AOA、AOB)和反硝化菌群落(nir S、nos Z)丰度均呈现先上升后下降的变化趋势。与对照相比,拔节期RS处理显著增加AOA、AOB、nirS和nosZ拷贝数,MS和WS处理对上述功能基因丰度均无显著影响。各生育期土壤NH₄⁺-N含量整体高于NO₃^–-N含量,二者均在水稻分蘖期达到峰...     

中国水蚀区5种典型土壤的侵蚀性降雨阈值比较

[目的]准确拟定侵蚀性降雨阈值,区分侵蚀性与非侵蚀性降雨事件,为有效减少土壤侵蚀预报的工作量以及区域土壤侵蚀防治提供科学参考。[方法]在北京市房山区布设中国5个水蚀二级区典型土壤休闲小区,收集各小区2006—2019年的产流产沙监测资料,利用降雨侵蚀力偏差法分析各小区的侵蚀性降雨量(P)和最大30 min雨强(I₃₀)阈值。[结果](1)相比P阈值,I₃₀在识别侵蚀性降雨方面更为有效。(2)黑土和褐土小区侵蚀性降雨阈值较高,二者P阈值均为10.0 mm,I₃₀阈值均为10.2 mm/h;黄土小区次之,其P和I₃₀阈值分别为9.5 mm和8.9 mm/h。紫色土与红壤小区较低,二者的P阈值分别为5.4和6.1 mm,I₃₀阈值分别为3.2和5.2 mm/h。(3)各径流小区的监测资料年限达到12 a时,侵蚀性降雨阈值才可达到稳定。[结论]不同地区土壤的侵蚀性降雨阈值存在较大差异。侵蚀性降雨阈值不仅受土壤自身特性如粒径分布和有机质含量的影响,还与当地的气候状况如降雨雨型有关。     

基于相对湿润度指数的西南地区季节性干旱时空分布特征

西南地区是中国重要农业生产区,季节性干旱是该区域最主要的农业气象灾害,研究季节性干旱时空分布特征对西南地区防旱减灾具有重要意义。该文收集西南地区4个省(市)共97个代表气象站50a(1959年-2008年)的逐日降水量、气温、日照时数、相对湿度、风速、水汽压等气象资料,选用国家标准中相对湿润度指数(M)作为干旱指标,以年、季为时间尺度,研究西南地区干旱频率和强度的空间分布特征,并分析近50a干旱强度和发生范围的年际变化规律。结果表明:西南地区年尺度干旱频率呈西部高,东部低的带状分布,高发区位于川西高原、川西南山地、云南西北部和中北部的山地、高原及河谷地带,发生频率在3年2遇以上;年干旱强度以中旱以上为主。不同季节干旱频率差异大:冬旱发生频率最高,春旱次之,秋旱较低,夏旱最低;干旱强度方面,冬旱强度最大,春旱次之,秋旱较小,夏旱最小;总体而言,干旱发生频率高的地方干旱强度也大。从年际变化看,西南地区总体上略有变湿的趋势,年干旱强度明显减弱,其中春旱、秋旱有减轻趋势,夏旱和冬旱有所增强;但近10a,年干旱强度增大明显,夏旱、秋旱、冬旱也明显上升,这与西南地区近几年干旱频繁发生相吻合。     

长期不同施肥下太湖地区稻田净温室效应和温室气体排放强度的变化

利用田间观测和模型预测方法对太湖地区一个长期不同施肥处理的稻田生态系统进行了稻季温室气体排放观测和净温室气体排放强度分析。结果表明,不同施肥管理下,稻田土壤有机碳含量不同程度提高,有机无机肥料配施较单施化肥处理显著提高有机碳库储量,并且秸秆处理略高于猪粪处理。与不施肥处理相比,长期施用肥料显著提高了稻田生态系统CH4和CO2的排放量,有机肥料与化肥配施较单纯施用化学肥料下土壤碳（CO2和CH4）排放增加,但化肥配施秸秆与化肥配施猪粪下稻田生态系统CH4和CO2的排放没有显著差异。不同施肥处理下,稻田生态系统净温室效应表现为CFM≈CFS〉CF〉NF,但水稻生产的净温室气体排放强度并没有显著性差异。因此,在提高水稻产量的同时,有机无机配合施肥并没有提高净温室气体的排放强度。     

春玉米田施用双氰胺和硫包衣尿素的节本减排效果分析

氧化亚氮（N2O）是一种重要的温室气体,农田土壤是其重要的排放源.本研究利用温室气体自动测定系统,对华北平原春玉米农田尿素（U）、尿素添加10％双氰胺（DCD1）、尿素添加5％双氰胺（DCD2）、硫包衣尿素（SCU）和不施肥（CK）5个不同施肥处理土壤进行N2O测定,以分析双氰胺和硫包衣尿素对土壤N2O排放的影响.结果表明,（1）各处理N2O排放总量顺序为U＞SCU＞ DCD2＞DCD1＞CK,各处理的排放系数在0.20％ ～0.71％,与单施尿素相比,DCD1、DCD2分别减少N2O排放59.5％、47.1％,硫包衣处理的N2O排放与尿素处理差异不显著,但两者的N2O排放均极显著高于添加DCD的处理（P＜0.01）.（2）排放高峰是伴随土壤孔隙含水量（WFPS）明显上升而发生的,各施肥处理N2O的排放通量与土壤WFPS呈极显著相关关系（P＜0.01）.（3） DCD2施肥方案每减排1tCO2-eq的同时可减少支出约178元,表明此方案可作为减少春玉米农田N2O排放的技术措施.     

间伐对杉木人工林土壤理化性质的季节影响

以南京市溧水林场实施了4种间伐强度（CK:0%、LIT:30%、MIT:50%、HIT:70%）的25 a生杉木人工林为研究对象,探讨了间伐7 a后0—20 cm土层的土壤温度、含水率、土壤全C、全N、全P,C/N和N/P的季节变化。结果表明,间伐对土壤理化性质的影响存在明显的季节差异性。春季,间伐对土壤温度、含水率和全C均无显著影响,MIT显著降低了土壤全N和全P的22%和26%,HIT显著降低了土壤全N的11%。夏季,间伐对土壤温度、全N、全P和N/P无显著影响,但3种间伐强度均显著提高了土壤含水率,平均为22%,MIT和HIT均显著降低了土壤全C和C/N。秋季,间伐对土壤理化性质的各个指标均有不同程度的显著影响。其中,3种间伐强度均显著提高了土壤温度、含水率、N/P,但显著降低了全P。冬季,间伐对土壤理化性质影响较小,除MIT显著降低了土壤温度而提高了土壤C/N及HIT显著提高了土壤全P外,间伐对其余指标均无显著影响。这些结果表明,在评价间伐对土壤理化性质影响时应考虑季节差异。间伐7 a后林内土壤全N和全P在一定程度上有所降低,尤其是土壤全P,建议在春季对LIT施适量的氮肥,对MIT施适量的氮肥和磷肥,在秋季对3种间伐处理施适量的磷肥,以提高土壤肥力促进林木生长。从土壤N和P年平均值来看,HIT最有利于保持林地的氮磷养分,LIT次之,MIT最差。     

不同比例尺数字高程模型对土壤侵蚀强度分级的影响

基于1∶5万和1∶50万2种不同比例尺的数字高程模型(DEM),结合土地利用类型、植被覆盖度等指标,对试验区土壤侵蚀强度进行了分级,并对不同比例尺DEM求算的坡度差异及其对土壤侵蚀强度分级的影响进行了分析。结果表明:1∶50万DEM较1∶5万DEM综合了大量信息,求算的坡度整体上偏小而使分级结果多集中在微度侵蚀区;不同地貌单元受DEM信息综合的影响不同,地形平坦的山前岗地区受影响最大,而地形复杂的中山区受影响相对较小。     

Species composition of arbuscular mycorrhizal fungi in two mountain meadows with differing management types and levels of plant biodiversity

Species composition of arbuscular mycorrhizal fungi (AMF) was analysed in two differently managed mountain grasslands in Thuringia (Germany). Arbuscular mycorrhizal fungi were studied in the roots of 18 dominant plant species from a total of 56 (32%). Additionally, spores of AMF were isolated from soil samples. Arbuscular mycorrhizal fungi species composition was analysed based on 96 sequences of the internal transcribed spacer of the nuclear ribosomal DNA, 72 originated from mycorrhizal roots, and 24 originated from AMF spores. Phylogenetic analyses revealed a total of 19 AMF species representing all genera of the Glomeromycota except Scutellospora and Pacispora. Despite a different farming intensity, resulting in remarkable differences concerning their plant species diversity (27 against 43 plant species), the diversity of AMF was found to be similar with 11 species on the intensively farmed meadow and ten species on the extensively farmed one. Nevertheless, species composition between both sites was clearly different. It thus seems likely that the AMF species composition, but not necessarily the species number, is related to above ground plant biodiversity in the system under study.     

黄土丘陵区不同降雨强度对农地土壤侵蚀的影响

采用人工模拟降雨的方法，对仪器自身性能进行了测试，并分设5种不同的降雨强度分别研究半干旱区林地、草地、人工草地和耕地的产流产沙特征。模拟天然降雨最大雨强5．05mm／min，雨量118．2～300．3mm／h；雨滴落地速度、雨滴动能等降雨特征值与天然降雨特征值是一致的；不同立地条件下径流量、侵蚀模数随雨强的增加而增加，并与降雨强度呈指数函数或幂函数关系。     

Effects of alternative tillage systems on soil quality and yield of spring cereals on silty clay loam and sandy loam soils in the cool, wet climate of central Norway

Tillage trials were established on a poorly drained silty loam overlying silty clay loam and on a freely drained sandy loam overlying medium sand, in 1988 and 1989, respectively. Autumn and spring ploughing and two ploughless systems were compared for 12–13 years, with three replications at each site. The ploughless treatments comprised deep versus shallow spring harrowing until 1999, and thereafter autumn plus spring harrowing versus spring harrowing only. In 6 years, treatments with and without fungal spraying of the cereal crops were included. In other years, fungicides were not used. Perennial weeds were controlled by herbicides as necessary, on nine occasions up until 2001. Average spring barley (Hordeum vulgare L.) and spring oat (Avena sativa L.) yields were similar with spring ploughing as with autumn ploughing at both sites. In treatments without ploughing, average yields on the silty loam over clay were 93% of those obtained with ploughing, and on the sandy loam over sand they were 81%. Smaller and non-significant yield differences were found between spring harrowing versus deep spring harrowing, and between autumn plus spring harrowing versus spring harrowing only. Fungal spraying increased yields markedly at both sites (25%), but there was no significant interaction between this treatment and tillage system. Oat was compared with barley in 2 years, with oat performing better under ploughless tillage. At both sites increases in penetrometer resistance occurred in the topsoil of unploughed treatments. These were considered particularly limiting on the sandy loam. On the silty loam there was an increase in surface horizon porosity in the absence of ploughing, which was associated with an increase in topsoil organic matter content. On this soil there was also a tendency toward lower penetrometer resistance at >30 cm depth on autumn plus spring harrowed soil than on ploughed soil, indicating that the plough pan may have diminished. This was supported by observations of greater earthworm activity on unploughed soil. Soil chemical analyses revealed that mineral N and plant-available P and K accumulated in the upper horizon under ploughless tillage. The percentage yields obtained in individual years with autumn as opposed to spring ploughing, were positively correlated with air temperature during 0–4 weeks after planting on the silty loam, and with precipitation during 0–12 weeks after planting on the sandy loam. In the case of yields obtained with spring harrowing only, relative to spring ploughing, positive correlations were found with 0–4 week temperature on both soil types, suggesting that low early season temperatures may limit yields under ploughless tillage.